High-entropy alloys with ultra-high tensile properties at room temperature and low temperature and their preparation methods

Abstract

This invention discloses a high-entropy alloy with ultra-high tensile properties at room temperature and low temperature, and its preparation method. The alloy is a Co-Ni-Cr-Al-Ti(B) high-entropy alloy. The alloy is prepared by casting, homogenization solution treatment, cold mechanical deformation treatment, and aging heat treatment. The alloy prepared by cold mechanical deformation and heat treatment exhibits a fully recrystallized microstructure with a multiphase, multi-principal-element L12 ordered structure. At room temperature (293K), the prepared alloy exhibits a uniform tensile plasticity of over 40% and a tensile strength of over 1.70 GPa. At liquid nitrogen temperature (77K), the prepared alloy sheet exhibits a uniform tensile plasticity of over 50% and a tensile strength of over 2.0 GPa, achieving a high degree of combination of plasticity and strength.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of high-performance alloy material preparation, and provides a CoCrNiAlTi(B) high-entropy alloy with super-high mechanical properties at room temperature (293K) and liquid nitrogen temperature (77K) and a preparation method thereof. BACKGROUND

[0002] The aerospace, low-temperature superconducting and other key national defense fields urgently need to update and replace structural materials with high mechanical properties at room temperature and low-temperature environments. High-strength and ductile metal profiles are the key to preparing aerospace low-temperature fuel storage and transportation equipment, and specific requirements are good service performance, excellent stress corrosion resistance, excellent dimensional stability and good processing process at low-temperature conditions. At present, austenitic stainless steel, nickel-based alloy or cobalt-based alloy is commonly used as a manufacturing material in engineering, but due to the inherent mutual exclusivity of strength and plasticity, the current performance has been optimized to the limit, and in particular, the combination of tensile strength and uniform plasticity is difficult to improve by leaps and bounds, thereby severely restricting the improvement space of the preparation of low-temperature fuel storage and transportation special equipment.

[0003] An important indicator of high-performance structural materials urgently needed in the aerospace, low-temperature superconducting and other key national defense fields is to have high yield strength and high uniform plasticity (significant work hardening phenomenon during deformation). The comprehensive improvement of yield strength and uniform plasticity determines the carrying capacity, fatigue resistance and safety of the structural material.

[0004] To improve the comprehensive mechanical properties at room temperature and low temperature, innovative design of advanced structural materials is required. Although the face-centered cubic structure alloy material has the ability to obtain high uniform plasticity, the yield strength is often low. For this reason, many new structural materials have been developed, among which the L12 ordered intermetallics, as a unique class of metallic materials, have attracted more and more research. Due to their excellent thermal stability, strong chemical bonding and low atomic activity, they have attracted widespread attention from the scientific and industrial communities. However, due to the difficulty in starting the slip system and / or the nature of the weak grain boundary of the stoichiometric L12 ordered intermetallics, they are usually brittle at ambient temperature, which seriously hinders their practical application in engineering systems. Existing research shows that the change of the chemical composition of the L12 ordered intermetallics, i.e., deviating from the stoichiometric ratio, can improve the plasticity of the intermetallic material, because of the local precipitation of face-centered cubic phase (FCC). The second method is to add grain boundary segregation element B to form a nanometer FCC layer on the grain boundary to toughen. Both methods make the alloy obtain toughening effect, but do not essentially stimulate the intrinsic plasticity of L12, so the strength and toughness of the alloy are still limited.

[0005] In this context, it is urgent to strengthen the basic research on high-entropy multi-principal element L12 type alloys, and to deeply explore their room temperature and low temperature performance potential, so as to develop new high-strength high-plasticity alloys with significant performance advantages. SUMMARY

[0006] In view of this, the present application provides a high-entropy multi-phase multi-principal element L12 type high-entropy alloy with ultra-high tensile properties at room temperature and low temperature environment and a preparation method thereof to solve the problems existing in the prior art.

[0007] The present application provides a high-entropy alloy with ultra-high tensile properties at room temperature and low temperature environment, according to atomic percentage, comprising the following components: Cr: 0-10%, Ni: 25-38%, Al: 3-7%, Ti: 8-12%, B: 0.5-1%, and the balance is Co.

[0008] Preferably, the high-entropy alloy with ultra-high tensile properties at room temperature and low temperature environment comprises the following components according to atomic percentage: Cr: 3-7%, Ni: 28-32%, Al: 5-7%, Ti: 8-12%, B: 0.5-1%, and the balance is Co.

[0009] The present application also provides a preparation method of a high-entropy alloy with ultra-high tensile properties at room temperature and low temperature environment, comprising the following steps:

[0010] (1) preparing the alloy according to the above components and atomic percentage and melting and casting into ingot;

[0011] (2) homogenizing the ingot to obtain a casting;

[0012] (3) solid solution heat treatment of the casting to obtain an alloy with multi-phase L12 structure ordered organization;

[0013] (4) cold rolling mechanical deformation of the casting after solid solution heat treatment with a deformation of 70-90% to obtain a plate;

[0014] (5) aging heat treatment of the deformed plate to obtain a high-entropy alloy plate with ultra-high tensile properties at room temperature and low temperature environment.

[0015] Preferably, in step (2), the homogenization temperature is 1150-1200℃, and the time is 6-24h.

[0016] Further preferably, in step (3), the solid solution heat treatment temperature is 900-1100℃, and the time is 4-8h.

[0017] Further preferably, in step (5), the aging heat treatment is a two-stage heat treatment, the first stage has a temperature of 1000-1200 DEG C and a time of 5-30 min; the second stage has a temperature of 600-700 DEG C and a time of 24-100 h.

[0018] The high-entropy alloy with ultrahigh tensile properties under room temperature and low temperature environment provided by the application is based on the design of multi-principal element CoNiTiCrAl(B) alloy, and a multi-phase multi-principal element L12 phase composite structure is obtained. The complex composition at the interface of different components of the L12 phase makes the interface present a local disordered state. This local disordered state avoids the brittleness of the interface and improves the bonding force of the interface. Meanwhile, in the process of plastic deformation, the local disordered state structure has a mutual coordination effect on the plastic deformation between different components of the multi-principal element L12 phase, so that the alloy has a higher uniform plastic deformation capacity while obtaining a higher yield strength.

[0019] The high-entropy alloy with ultrahigh tensile properties under room temperature and low temperature environment provided by the application has a uniform tensile plasticity of more than 40% and a tensile strength of more than 1.70 GPa under room temperature conditions (293 K). The uniform tensile plasticity of the prepared alloy sheet is more than 50% and the tensile strength is more than 2.0 GPa under liquid nitrogen temperature conditions (77 K), so that the plasticity and strength are highly combined. BRIEF DESCRIPTION OF DRAWINGS

[0020] The application will be further described in detail below in combination with the drawings and embodiments:

[0021] Figure 1 Typical tensile curves of the alloy of Example 1 under room temperature and liquid nitrogen temperature conditions;

[0022] Figure 2 Typical recrystallization microstructure diagram of the alloy of Example 1. DETAILED DESCRIPTION

[0023] The application will be further explained below in combination with specific embodiments, but is not limited to the application.

[0024] Although the single-phase L12 multi-principal element high-entropy alloy has certain advantages in developing high plasticity alloys, the development of alloys with high strength and good uniform plasticity at room temperature and low temperature is still in the bottleneck stage.

[0025] The application provides a high-entropy alloy with ultrahigh tensile properties under room temperature and low temperature environment, which comprises the following components according to atomic percentage: Cr: 0-10%, Ni: 25-38%, Al: 3-7%, Ti: 8-12%, B: 0.5-1%, and the balance is Co.

[0026] As an improvement to the technical solution, the high-entropy alloy with ultra-high tensile properties at room temperature and low temperature includes the following components by atomic percentage: Cr: 3-7%, Ni: 28-32%, Al: 5-7%, Ti: 8-12%, B: 0.5-1%, with the balance being Co.

[0027] This invention also provides a method for preparing a high-entropy alloy with ultra-high tensile properties at room temperature and low temperature, comprising the following steps:

[0028] (1) Prepare the alloy according to the above composition and atomic percentage and melt and cast it into an ingot;

[0029] (2) The ingot is homogenized to obtain a casting;

[0030] (3) The casting is subjected to solution heat treatment to obtain an alloy with an ordered structure of multiphase L12;

[0031] (4) The castings after solution heat treatment are subjected to cold rolling mechanical deformation with a deformation amount of 70-90% to be rolled into plates;

[0032] (5) The deformed plate is subjected to aging heat treatment to obtain a high-entropy alloy plate with ultra-high tensile properties at room temperature and low temperature.

[0033] As an improvement to the technical solution, in step (2), the homogenization treatment temperature is 1150-1200℃ and the time is 6-24h.

[0034] As an improvement to the technical solution, in step (3), the temperature of the solution heat treatment is 900-1100℃ and the time is 4-8h.

[0035] As an improvement to the technical solution, in step (5), the aging heat treatment is a two-stage heat treatment. The temperature of the first stage is 1000-1200℃ and the time is 5min-30min; the temperature of the second stage is 600-700℃ and the time is 24-100h.

[0036] The high-entropy alloy with ultra-high tensile properties at room temperature and low temperature provided by this invention, after cold mechanical deformation and heat treatment, is characterized by a fully recrystallized structure with a multiphase, multi-principal L12 ordered structure. The complex composition at the interface of different L12 phases results in a local disordered state at the interface. This local disordered state avoids the brittleness of the interface and improves the bonding force of the interface. At the same time, during plastic deformation, this local disordered structure has a mutual coordinating effect on the plastic deformation between the multiphase, multi-principal L12 phases with different compositions, so that the alloy can obtain high yield strength and high uniform plastic deformation capacity.

[0037] Example 1

[0038] Formulated into Co 49 Ni 30 Cr5Al5Ti 10 B1 (at.%) alloy was melted into 2 kg ingots in a vacuum induction furnace, homogenized at 1200℃ for 6 h, and then solution treated at 1000℃ for 8 h. It was then cold-rolled at room temperature with a deformation of approximately 80%, followed by heat treatment at 1150℃ for 5 min + 600℃ for 48 h.

[0039] The resulting alloy was subjected to temperature variations of 10°C at both room temperature and liquid nitrogen temperature. -3 s -1 The material was stretched at a certain stretching rate. At room temperature, the elongation was 40%, the tensile strength was 1720 MPa, and the yield strength was 1110 MPa. At liquid nitrogen temperature, the elongation was 52%, the tensile strength was 2024 MPa, and the yield strength was 1210 MPa. Figure 1 These are typical tensile curves of the alloy sheet at room temperature and liquid nitrogen temperature. Figure 2 This is a typical recrystallization microstructure diagram of the alloy sheet.

[0040] Example 2

[0041] Formulated into Co 47 Ni 28 Cr7Al5Ti 12 B1 (at.%) alloy was melted into 2 kg ingots in a vacuum induction furnace, homogenized at 1200℃ for 6 h, and then solution treated at 1000℃ for 8 h. It was then cold-rolled at room temperature with a deformation of approximately 80%, followed by heat treatment at 1150℃ for 5 min + 600℃ for 48 h.

[0042] The resulting alloy was subjected to temperature variations of 10°C at both room temperature and liquid nitrogen temperature. -3 s -1 The material was stretched at a certain stretching rate. At room temperature, the elongation was 40%, the tensile strength was 1720 MPa, and the yield strength was 1110 MPa. At liquid nitrogen temperature, the elongation was 52%, the tensile strength was 2024 MPa, and the yield strength was 1210 MPa.

[0043] Example 3

[0044] Formulated into Co 47.5 Ni 32 Cr5Al7Ti8B 0.5The (at.%) alloy was melted into 2 kg ingots in a vacuum induction furnace, homogenized at 1150℃ for 12 h, and then solution treated at 1100℃ for 4 h. It was then cold-rolled at room temperature with a deformation of approximately 70%, followed by heat treatment at 1000℃ for 30 min + 650℃ for 24 h.

[0045] The resulting alloy was subjected to temperature variations of 10°C at both room temperature and liquid nitrogen temperature. -3 s -1 The material was stretched at a certain stretching rate. At room temperature, the elongation was 40%, the tensile strength was 1710 MPa, and the yield strength was 1100 MPa. At liquid nitrogen temperature, the elongation was 53%, the tensile strength was 2067 MPa, and the yield strength was 1250 MPa.

[0046] Example 4

[0047] Formulated into Co 45.5 Ni 32 Cr7Al5Ti 10 B 0.5 The (at.%) alloy was melted into 2 kg ingots in a vacuum induction furnace, homogenized at 1200℃ for 24 h, and then solution treated at 1100℃ for 16 h. It was then cold-rolled at room temperature with a deformation of approximately 90%, followed by heat treatment at 1200℃ for 5 min + 700℃ for 100 h.

[0048] The resulting alloy was subjected to temperature variations of 10°C at both room temperature and liquid nitrogen temperature. -3 s -1 The material was stretched at a certain stretching rate. At room temperature, the elongation was 35%, the tensile strength was 1700 MPa, and the yield strength was 1100 MPa. At liquid nitrogen temperature, the elongation was 50%, the tensile strength was 2050 MPa, and the yield strength was 1250 MPa.

Claims

1. A method for preparing high-entropy alloys with ultrahigh tensile properties at room and cryogenic temperatures, characterized in that: The high-entropy alloy with ultrahigh tensile property under room temperature and low temperature environment comprises the following components in atomic percentage: Cr: 0-10%, Ni: 25-38%, Al: 3-7%, Ti: 8-12%, B: 0.5-1%, and the balance is Co. The preparation method of the high-entropy alloy with ultrahigh tensile property under room temperature and low temperature environment comprises the following steps: (1) preparing the alloy according to the components and melting and casting into ingot; (2) homogenizing the ingot to obtain a casting, wherein the homogenizing temperature is 1150-1200℃, and the time is 6-24h; (3) solid solution heat treatment of the casting, wherein the solid solution heat treatment temperature is 900-1100℃, and the time is 4-8h; (4) cold rolling mechanical deformation of the casting after solid solution heat treatment with a deformation of 70-90% to roll into a plate; (5) aging heat treatment of the deformed plate to obtain the high-entropy alloy plate with ultrahigh tensile property under room temperature and low temperature environment, wherein the aging heat treatment is two-stage heat treatment, the first stage temperature is 1000-1200℃, and the time is 5min-30min; the second stage temperature is 600-700℃, and the time is 24-100h.

2. The method of claim 1, wherein the high-entropy alloy having ultrahigh tensile properties at room and cryogenic temperatures is prepared by the steps of: The high-entropy alloy with ultrahigh tensile property under room temperature and low temperature environment comprises the following components in atomic percentage: Cr: 3-7%, Ni: 28-32%, Al: 5-7%, Ti: 8-12%, B: 0.5-1%, and the balance is Co. ​

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